Add RBF-bumping of preimage/timeout txn on remote HTLC outputs

Given they are only signed by us we can RBF at wish

Fix tests broken by introduction of more txn broadcast
(channel_monitor_network_test)

Author: Antoine Riard

src/ln/channelmonitor.rs

@@ -2579,7 +2579,10 @@ impl ChannelMonitor {
 					inputs_witnesses_weight += Self::get_witnesses_weight(if !is_htlc { &[InputDescriptors::RevokedOutput] } else if script.len() == OFFERED_HTLC_SCRIPT_WEIGHT { &[InputDescriptors::RevokedOfferedHTLC] } else if script.len() == ACCEPTED_HTLC_SCRIPT_WEIGHT { &[InputDescriptors::RevokedReceivedHTLC] } else { &[] });
 					amt += *amount;
 				},
-				&TxMaterial::RemoteHTLC { .. } => { return None; },
+				&TxMaterial::RemoteHTLC { ref preimage, ref amount, .. } => {
+					inputs_witnesses_weight += Self::get_witnesses_weight(if preimage.is_some() { &[InputDescriptors::OfferedHTLC] } else { &[InputDescriptors::ReceivedHTLC] });
+					amt += *amount;
+				},
 				&TxMaterial::LocalHTLC { .. } => { return None; }
 			}
 		}
@@ -2611,7 +2614,20 @@ impl ChannelMonitor {
 					bumped_tx.input[i].witness.push(script.clone().into_bytes());
 					log_trace!(self, "Going to broadcast bumped Penalty Transaction {} claiming revoked {} output {} from {} with new feerate {}", bumped_tx.txid(), if !is_htlc { "to_local" } else if script.len() == OFFERED_HTLC_SCRIPT_WEIGHT { "offered" } else if script.len() == ACCEPTED_HTLC_SCRIPT_WEIGHT { "received" } else { "" }, vout, txid, new_feerate);
 				},
-				&TxMaterial::RemoteHTLC { .. } => {},
+				&TxMaterial::RemoteHTLC { ref script, ref key, ref preimage, ref amount } => {
+					let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
+					let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[0], &script, *amount)[..]);
+					let sig = self.secp_ctx.sign(&sighash, &key);
+					bumped_tx.input[0].witness.push(sig.serialize_der().to_vec());
+					bumped_tx.input[0].witness[0].push(SigHashType::All as u8);
+					if let &Some(preimage) = preimage {
+						bumped_tx.input[0].witness.push(preimage.clone().0.to_vec());
+					} else {
+						bumped_tx.input[0].witness.push(vec![0]);
+					}
+					bumped_tx.input[0].witness.push(script.clone().into_bytes());
+					log_trace!(self, "Going to broadcast bumped Claim Transaction {} claiming remote htlc output {} from {} with new feerate {}", bumped_tx.txid(), vout, txid, new_feerate);
+				},
 				&TxMaterial::LocalHTLC { .. } => {
 					//TODO : Given that Local Commitment Transaction and HTLC-Timeout/HTLC-Success are counter-signed by peer, we can't
 					// RBF them. Need a Lightning specs change and package relay modification :

src/ln/functional_tests.rs

@@ -1718,8 +1718,10 @@ fn channel_monitor_network_test() {
 	// nodes[3] gets the preimage, but nodes[2] already disconnected, resulting in a nodes[2]
 	// HTLC-Timeout and a nodes[3] claim against it (+ its own announces)
 	nodes[2].node.peer_disconnected(&nodes[3].node.get_our_node_id(), true);
+	let node2_commitment_txid;
 	{
 		let node_txn = test_txn_broadcast(&nodes[2], &chan_3, None, HTLCType::TIMEOUT);
+		node2_commitment_txid = node_txn[0].txid();
 
 		// Claim the payment on nodes[3], giving it knowledge of the preimage
 		claim_funds!(nodes[3], nodes[2], payment_preimage_1);
@@ -1753,6 +1755,16 @@ fn channel_monitor_network_test() {
 			nodes[3].chain_monitor.block_connected_checked(&header, i, &Vec::new()[..], &[0; 0]);
 		}
 
+		// Clear bumped claiming txn spending node 2 commitment tx. Bumped txn are generated after reaching some height timer.
+		{
+			let mut node_txn = nodes[3].tx_broadcaster.txn_broadcasted.lock().unwrap();
+			node_txn.retain(|tx| {
+				if tx.input[0].previous_output.txid == node2_commitment_txid {
+					false
+				} else { true }
+			});
+		}
+
 		let node_txn = test_txn_broadcast(&nodes[3], &chan_4, None, HTLCType::TIMEOUT);
 
 		// Claim the payment on nodes[4], giving it knowledge of the preimage